Wednesday, 28 February 2018

Psophocarpus lancifolius - Mysterious Misobwa

One of the joys of doing a botany degree (back when it was still possible in the UK, happy days) was the opportunity for a little bit of extracurricular reading down between the shelf stacks. First port of call was always the purple-bound volumes of  Economic Botany. Many an hour of sweet happiness was spent engaged in that noblest of activities.

On one such occasion, I picked a random volume, opened it at a random page and was soon captivated; the enigmatic tale of an undervalued Afromontane legume unfolded, a crop wild relative of the winged bean (Psophocarpus tetragonolobus) known, at least sometimes, as misobwa (P. lancifolius). Oh - and it had edible roots too.

The Afromontane zones, with their high mountains, dense jungles, miombo woodlands, swamps and dambo grasslands have always appealed to my inner armchair explorer. Likewise, I've always found crop wild relatives intriguing, both in their own right and as the source of disease and drought resistance, among other useful qualities. Where would wheat, tomatoes and innumerable other crops be without them?  So, with misobwa's double whammy hitting me in all the right places, I knew it was time to roll with the blows, stiffen my sinews and start searching; this plant would surely be a worthy addition to my bucket list, filed under the category 'roots to know and grow'.

At this juncture, I really should acknowledge my sources; I complain enough about others who fail to do so. Most of what I know about misobwa comes from the following paper:

Uses, nutritional composition and ecogeography of four species of Psophocarpus (fabaceae, phaseoleae) in Zaire

By Daniel Harder, Oneyembe Pend Mbutu Lolema and Musasa Tshisand

According to Harder et al, misobwa grows at altitudes up to around 2500 metres above sea level in the Democratic Republic of the Congo; this is a bit higher than its close relative, the winged bean, which usually runs out of steam at around 2000 metres, although it sometimes struggles a  little higher in Papua New Guinea before chilling and frost finish it off.  I generally take an elevation of around 3000 metres in the tropics as my sweet spot for a sporting chance that a plant might make it here outdoors in Cornwall during the summer. Being a soft-hearted soul, I'm always prepared to exercise a little latitude in the application of my altitude rule, however - if a plant has some other merits. Misobwa - in my opinion at least - does.

What merits, you ask? Well, by all accounts its tubers are an outstanding food, containing around 10% protein and 5% lipid. But don't take my word for it. To quote that paper yet again:

The nutritious tuber is comparable to the seeds of soybean and peanut for protein and to soybean, peanut, and winged bean for lipids; it has a medium to low complement of carbohydrate (Smartt 1976). The tubers of P. lancifolius constitute an excellent food source and, as such, are promising in tropical areas experiencing seasonal rains.

You would hardly expect me to refrain from a madcap misobwa chase after that kind of write-up. Resistance is futile in the face of the Borg of tuberous beans. My peanut growing attempts have been pitiful and my soya beans' performance always so-so. Here was a root from the family Fabaceae that might just help me to regain my self-respect, I thought. 

Not only does the misobwa plant form carrot-shaped, edible roots with the properties described above, but its long, rambling stems will also root at the nodes where they touch the ground and form secondary tubers. Under cultivation, might it be possible to persuade the plants to produce more tubers by pegging the vines down?

But aren't we missing something here?  It's all very well to concentrate on a plant's apparent virtues as a crop,  but what does it actually taste like? Daniel, for all his evident enthusiasm, doesn't mention this. Luckily I have some idea, thanks to this book, which I discovered online:

Pygmées d'Afrique Centrale, by Stefan Seitz

It's an ethnobotanical treatise on, well, I think you can guess if your fluency in French is equal to or greater than mine. 

Anyway, it seems that the Bashi and Barwha peoples eat misobwa roots, which are said to resemble a potato in taste and are relished after cutting up and grilling. They gather the roots from open country rather than the rainforest proper. Although sketchy, this at least indicates that misobwa is not only edible, but palatable too. Again, this is an endearing tendency in a world populated by foul flavoured impostors like mashua (Tropaeolum tuberosum). Make that a triple whammy. 

Until 2016 this was pretty much the sum total of my knowledge about misobwa; then, after years - decades - of vainly searching, letter writing and emailing, I finally got lucky. My seeds came not from the DCR, but by a rather unexpectedly circuitous route: from Zimbabwe, via Australia. It seems that they were collected in the 1980s near Harare, by the banks of the Umwindsi River which wends its way through the area around Gaydon Road. And, perhaps disappointingly, they were collected at an altitude of only 1480 metres, although this is about 15 degrees further from the equator than the Congo sites, so average temperatures ought to be commensurately lower.

Eventually it's time to move on from all the the book learning and received wisdom and actually get up close and personal with a plant in real time.  How exactly did I get on with my first misobwa crop?

I received the aforementioned seed rather late in the year, towards the end of May. Germination was good, but that year I was caught short on the greenhouse front, so I grew them on the very
windowsill, where, a few years earlier, I had grown my asbin.
Misobwa seeds, left; winged bean/asbin right
According to Daniel Harder, the whole misobwa plant is frequently covered in dense yellow hairs. I was rather disappointed that my plants seemed completely hairless. In fact, they looked very similar to talet (Amphicarpaea bracteata), with the same twining habit of growth and trifoliate leaves. I needed some reassurance that what I had was the real McCoy and not some cheap impersonator. It's been claimed by some that I have 'trust issues'; I can't comment on that, but I do like to know the true identity of the plants I'm growing. One distinctive characteristic of Psophocarpus lancifolius seeds is that they are described as having "a hilum which transversely bisects the pale, broadly elliptical aril". Taking my faithful hand lens, I looked at the remaining seeds and could see that this was true: my plants were indeed misobwas - clean-shaven Zimbabwean versions, maybe, but misobwas just the same, no mistaking it.

Misobwa seedlings have a typical trifoliate leaves and a slightly kinked, zig -zag habit of growth which you may be able to make out in this picture:

Misobwa seedlings with zig-zag growth habit
They grew away quite well, creating a sinuous tangle of leafy, twining stems. With a little leap of imagination I could see myself squelching through a wet dambo grassland, with the lofty peaks of the Virunga National Park looming in the background. Stooping to examine a ripe misobwa pod, I could hear a silverback gorilla drumming on his chest somewhere in the undergrowth.  Like I said, I'm an experienced armchair traveller.
My very own entangled misobwa thicket
Back to the real world. I waited, patiently, for flowers to appear, but sadly, they never did. Towards the end of January 2017, the spell was broken and my beloved plants were starting to look a bit sorry for themselves, with withered leaves coated by sticky, aphidly secretions which really marred their appearance. I made the executive decision to tip them out of their pots and see what, if anything they'd made underground.

Here's the result:
Misobwa roots. Small and fleshy. 
Thickened roots were indeed present. These were, as predicted, carrot shaped, but more the size and colour of a stunted wild carrot's tap root than a chunky Autumn King. I saw no signs of nodulation, so I'm guessing that the correct cowpea miscellany rhizobia were absent. Neither a triumph nor a tragedy, these roots looked like they might be tasty roasted, but I rather doubted it would be worth the effort. Alas and alack - my attempts to overwinter them were a failure and I now wish I'd followed my baser instincts and eaten them straight away. 

As is so often the case, my initial misobwa cultivation attempt raised more questions than it answered. Here are a few that spring to mind: what controls storage root  development and size? How can I persuade plants to flower? And does anyone know anyone who can collect me some seeds from the highest parts of misobwa's range in Congo, Rwanda or Burundi? Maybe together we can explore the mysteries of this enigmatic root, a gift from the lovely, troubled highlands of equatorial Africa.  

Sunday, 8 May 2016

Got My Finger on The Pulses: The Trifoliate Triumvirate

Every year is, it seems, International Year of something or other. The cynic in me sometimes struggles with the overstimulating and diluting effect of this continual bombardment.

This year, is different, however: it's International Year of Pulses. Where would we be without beans? It seems like there's a bean or pea for everywhere, from everywhere; as readers of this blog may recall, my flexible use of the word 'root', has allowed the occasional geocarpic legume to storm the ramparts of Castle Radix in the past. No point stopping now.

My enthusiasm for talet (Amphicarpaea bracteata) is well-known and I'll come to my reasons for initiating another sowing session in due course. After some deliberation and in defiance of the impressively unpromising spring we've had, I've decided to give fate the finger and try a couple of other interesting underground legumes. So, my fellow rhizophiles, I give you my 2016 Trifoliate Triumvirate: Amphicarpaea bracteata, Arachis monticola and Vigna subterranea.

My Trifoliate Triumvirate: top left: Amphicarpaea bracteata; top right: Vigna subterranea; bottom right: Arachis monticola
Arachis monticola is probably the progenitor of the modern peanut (A. hypogaea) with which we are all familiar. The tetraploid love child of two diploid species, A. monticola, clearly a mountain lover, has appealed to me for years. It comes from the area around Jujuy in Argentina and grows at altitudes between 1300-2300 metres in the Andes. A bit of cursory research shows that A. monticola, lurking in its high mountain fastness, prefers noticeably cooler temperatures than other wild peanuts, or tolerates them at least. With a hope that never dies, my thinking is that we might be able to coax the peanut to boldy grow where it's never grown before. This chill tolerance, if true, sounds very promising, especially when its ability to cross with A. hypogaea, the cultivated peanut, is taken into account: consider the Cornish Peanut Improvement Programme duly initiated.

There's a downside, of course - this is a crop wild relative, not an actual crop, after all. The peanuts that A. monticola produces are small and the plant distributes them far and wide, so harvesting them will be a pain. That said, I expect the rodents will manage to demolish the lot with their usual aplomb.

A. monticola, diminutive monkey nuts
A. monticola, diminutive seeds
In a beautifully timed coincidence, A. ipaensis, one of the long lost parents of the peanut, has just been rediscovered. In the world of crop wild relatives, this is a big deal. The big deal in my part of the world will be whether I can get my A. monticola seeds to germinate or not and whether they'll survive our summer. Here's hoping.

If you want to know more about peanut wild relatives, including Arachis monticola, here's a good paper to start with:
Biogeography of wild Arachis (leguminosae): distribution and environmental characterisation 

For more on the fascinating sex life of the peanut and its close relatives, you could have a look at this:
Genomic relationships between the cultivated peanut (Arachis hypogaea, Leguminosae) and its close relatives revealed by double GISH

Next up, is my wild card, Bambara groundnut (Vigna subterraneana), which I chose, not for its lofty altitude of origin, chill tolerance or any other possible pre-adaptations to life in Cornwall, but because I've never grown it before and I fancied an experiment. The beans come in all sorts of colours and the  diverse batch I received looks like leguminous dolly mixture.
Vigna subterranea
Vigna subterranea is one of those intriguing African crops which has been rather eclipsed by New World invaders, in this case the peanut. It is still widely cultivated, however and has many merits, not least its resistance to high temperatures and drought, as one might expect given its origins in West Africa, probably in the hot dry parts of north eastern Nigeria. Those don't sound much like the climatic challenges we usually face here in Cornwall, but no less an authority than William Woys Weaver claims that there's a basic rule of thumb: if you can grow outdoor tomatoes, you can grow Vigna subterranea. Given the spectacular levels of Phytophthora infestans on our plot, which carries off our outdoor tomatoes and potatoes every year, this is but little comfort. He's referring to temperature, of course, rather than pathogen load; the way I see it, nothing ventured, nothing gained.  And you never know, a cold spring does not guarantee an indifferent summer. It might even encourage me to finally read this:

The mature beans are eaten roasted or boiled and are considered a complete food, containing about 65% carbohydrate, 18%  balanced protein and 6.5% fat; bambara groundnut milk is said to be more palatable than soya milk, which can only be a good thing. In terms of bean distribution, it looks like the plants have abandoned their wild child ancestral habits and deposit their pods demurely, close to the base of the plants. For that the voles will be duly grateful.

Last but no means least, I give you talet (Amphicarpaea bracteata), tried and tested in our climate. Following on from the success of that trial, I was heartbroken when, a few weeks later, a pheasant plucker emptied the pots, scattered the labels and pretty much gobbled the entire crop, eliminating several varieties in the process. Not so fast, Mr Pheasant! All is not lost, due to talet's cunning amphicarpic strategy, whereby it hedges its bets through the production of different types of seeds, including hard, long-lived ones. I've kept a stash of the latter type of all my varieties in case of just such an eventuality. Time to open it and resurrect those that were lost. I'll give the finger to a pheasant just as soon as I will to fate.
Sprouting subterranean talets (Amphicarpaea bracteata)
My talet resurrection enthusiasm knows no bounds. I've been inspired to open the dusty Radix crypt and disinter some seeds of varieties I placed there at the end of last century, when I first started tinkering with the plant in earnest. Are they still viable, after nearly twenty years?  If I have the time, I'd also like to get my head around the latest research which identifies three cryptic species within Amphicarpaea bracteata sensu lato and try and see which ones I've got. Help! Can I possibly cope with yet another trifoliate triumvirate?

Sunday, 24 January 2016

Oh Heck, it Ain't Mecha-meck!

During my blog's fallow phase, a few brave souls have continued to leave comments. I've just been moderating and publishing them. Turns out there were some interesting ones, but what really caught my attention was a message from Ron Kushner. Ron is an authority on all things Ipomoea -  I am a mere dilettante.  So when he politely lets me know that the seeds I received in good faith as I. pandurata, with their fabulously weirdy-beardy appearance, are in fact I. macrorhiza, I listen.

Just like the chuckle-inducing Corrections and Clarifications section in the Grauniad (sic), I am going to have to make a retraction. When I said "oh heck, here's mecha-meck", I was wrong. What I should have said is "oh heck, it's from Yucatan". 

It seems that I. macrorhiza has a distinctly southerly distribution, being found on the coast in the south eastern states of the USA. One theory is that it was transported there from Mexico by First Nations people, possibly as a food source. I. pandurata is found much further north and, by inference, ought to be a lot hardier than the southern softie that is I. macrorhiza.

The proof, as Ron has pointed out, lies in the seeds. Compare and contrast: 

Here's 'my' mecha-meck: an artisan-brewing, kimchi-gobbling hipster with splendid and extravagant whiskers:

Ipomoea macrorhiza

The true mecha-meck is more of a designer stubble aficionado:
Ipomoea panudurata (image courtesy of University of Missouri)

I suppose this late onset revelation is actually a bit of a relief; the impostor's growth and winter survival was, let's face it, a big disappointment. Without reworking the tired Spartacus allusion yet again, I'd rather the true mecha-meck reveal itself and we can all get on with our lives. 

On that note, in true one-step-forwards-two steps-back fashion, I must now throw myself on the tender mercies of East Coast USA rhizophiles.  Say, can anyone provide me with seeds of the true mecha-meck? 

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